Tissue oxygenation is an important physiological parameter in at least some instances. Abnormal oxygenation of tissues and blood is implicated in a number of diseases preceding tissue damage, including infectious processes, diabetic retinopathy, choroidal disorders, stroke and cancer. For instance, the retinal vasculature's oxygen saturation (SO2) is a valuable indicator of disease, in particular for patients with diabetic retinopathy (DR) who may experience changes in retinal oxygen saturation during their lifetime. A broad range of studies have shown that the earliest detectable sign of DR is an increase of ˜4% in the SO2 in the retinal veins. Once DR is detected, there are treatment options available to slow or stop DR progression and prevent retinal structural damage. The Early Treatment Diabetic Retinopathy Study (ETDRS), a multicenter clinical trial funded by the NEI, aims to determine whether the progress of DR could be slowed or stopped using either argon laser photocoagulation or aspirin treatment. Although a number of experimental systems aimed at measuring retinal SO2 have been developed, a reliable, robust model for in vivo monitoring is still lacking.
Prior methods and apparatus of measuring oxygenation of the tissue can be less than ideal. The prior methods and apparatus can be more complex and less accurate than would be ideal, and may not be well suited for tissue oxygenation mapping. For example, tissue can move and degrade measurements and the prior methods and apparatus can be less than ideally suited to measure tissue quickly. Measurements of retinal tissue of the eye can be subject to movement when the eye moves, and ocular measurements of the retina can be more difficult and less accurate than would be ideal.
In light of the above it would be desirable to have improved measurements to measure oxygenation of tissue.